Elastic strain engineering of defect doped materials

ABSTRACT

Compositions and methods related to straining defect doped materials as well as their methods of use in electrical circuits are generally described.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/585,308, filed Sep. 27, 2019, which claims benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 62/744,836, filed Oct.12, 2018, each of which is incorporated herein by reference in itsentirety for all purposes.

GOVERNMENT SPONSORSHIP

This invention was made with Government support under Grant No.N00014-17-1-2661 awarded by the Office of Naval Research. The Governmenthas certain rights in this invention.

TECHNICAL FIELD

Compositions and methods related to elastic strain engineering of defectdoped materials are generally described.

BACKGROUND

A material with an electronic bandgap much greater than its thermalfluctuation energy will often not have enough charge carriers (e.g.,electrons and/or holes) to function as a semiconducting material.Instead, to function, the material may include defects with additionallocalized electronic states whose energies are inside the electronicbandgap of the material, but proximate to the edges of the conductionband minimum and/or the valence band maximum. If the energy-differencebetween the localized electronic states of the defect and either theconduction band minimum or the valence band maximum is sufficientlysmall, then it is possible for the defects to be ionized by thermalfluctuation energy. In such cases, a localized electron around thedefect either: (i) makes a transition from the aforementioned localizedelectronic state to the delocalized conduction band state (n-doping); or(ii) captures a delocalized valence band electron and becomes thelocalized electronic state, thereby creating a delocalized hole in thevalence band (p-doping). When the energy difference is large, however,thermal fluctuation energy at room temperature may not be sufficient toionize a defect to form charge carriers.

SUMMARY

Compositions and methods related to elastically straining defect dopedmaterials are generally described.

In certain embodiments, a composition includes a defect doped material,wherein a strain is applied to a least a portion of the defect dopedmaterial. The defect doped material may be a non-conducting materialwhen the defect doped material is in an unstrained state, and the defectdoped material may be a semiconducting material or a conducting materialwhen the strain is applied to the defect doped material.

According to some embodiments, a method includes controlling aconductive state of a defect doped material. The method may includeapplying a strain to at least a portion of the defect doped material,and transitioning the defect doped material from a non-conductivematerial to a semiconducting material or a conducting material.

In certain embodiments, an electrical circuit may include a defect dopedmaterial forming at least a portion of the electrical circuit, and anactuator configured to selectively strain the defect doped material. Thedefect doped material may be a non-conducting material when the defectdoped material is in an unstrained state, and the defect doped materialmay be a semiconducting material or a conducting material when thedefect doped material is selectively strained by the actuator.

It should be appreciated that the foregoing concepts, and additionalconcepts discussed below, may be arranged in any suitable combination,as the present disclosure is not limited in this respect. Further, otheradvantages and novel features of the present disclosure will becomeapparent from the following detailed description of various non-limitingembodiments when considered in conjunction with the accompanyingfigures.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures may be represented by a like numeral. Forpurposes of clarity, not even component may be labeled in even drawing.In the drawings:

FIG. 1A is, according to some embodiments, a schematic representation ofa conventional change in energy difference between a localizedelectronic state of a defect and an excited electronic state of adefect:

FIG. 1B is, according to some embodiments, a schematic representation ofa change in energy difference between a localized electronic state of adefect and an excited electronic state of a defect due to theapplication of strain;

FIG. 2 is, according to some embodiments, a cross-sectional schematicrepresentation of a non-limiting defect doped material;

FIG. 3 is, according to some embodiments, a cross-sectional schematicrepresentation of a non-limiting defect doped material disposed on asubstrate;

FIG. 4 is, according to some embodiments, a cross-sectional schematicrepresentation of a non-limiting defect doped material disposed on asubstrate comprising a recess,

FIG. 5 is, according to some embodiments, a cross-sectional schematicrepresentation of a non-limiting actuator and defect doped materialdisposed on a substrate;

FIG. 6 is, according to some embodiments, a cross-sectional schematicrepresentation of a non-limiting defect doped material forming at leasta portion of a circuit;

FIG. 7 is, according to some embodiments, a flow chart describing amethod of controlling a conductive state of a defect doped material;

FIG. 8 is, according to some embodiments, an exemplary drawing of thebreaking of tetrahedral symmetry in diamond comprising a nitrogendefect;

FIG. 9 is, according to some embodiments, a graph of an energy barrieras a function of strain; and

FIG. 10 is, according to some embodiments, a plot of the strain gradientfrom an asymmetrical orientation to a symmetrical orientation fordiamond comprising a nitrogen defect.

DETAILED DESCRIPTION

Materials with a wide bandgap often do not have enough charge carries(e.g., holes and/or electrons) in order to function as semiconducting orconducting materials. For example, the implementation of diamond, anultra-wide bandgap material, as a semiconducting or conducting materialhas conventionally been unsuccessful due to the difficulty ineffectively doping the material with a defect capable of producingelectrons (e.g., a n-type dopant). In some materials, a substitutionaldefect in the material may spontaneously break symmetry from one or morelocalized electronic states to one or more non-degenerate low-symmetryvariant electronic states Such a spontaneous break in symmetry resultsin a material with a deep dopant state that has an energy far below(e.g., greater than or equal to 1 eV below) the conduction band edge orabove the valence band edge. The energy of activation to ionize a defectin a deep dopant state is too large to be facilitated byroom-temperature thermal fluctuations. Furthermore, depending on thechoice of defect, the energy of activation of the defect to overcome theenergy gap from the one or more localized electronic states to eitherthe conduction band edge or the valance band edge can vary greatlywithin the same material. In a material comprising diamond, forinstance, the energy of activation of a p-type dopant can differ byapproximately 200 meV from the energy of activation of an n-type dopant.As a result, a defect in a deep dopant state typically does notcontribute charge carriers to the conduction band and/or valence band,resulting in a material that is incapable of being used in asemiconducting or conducting device. Thus, the Inventors have recognizeda need for methods and systems to further alter the properties of widebandgap materials to facilitate their use in a semiconducting and/orconducting device.

In view of the above, the Inventors have realized and appreciated thatelastic strain can be used to control the doping level in a defect dopedmaterial. In certain embodiments, a defect may transition from a deepdopant state to a shallow dopant state upon the application of anelastic strain. For example, as strain is applied to the defect dopedmaterial, the transition of a defect from a deep dopant state to ashallow dopant state may occur due to a decrease in the energy ofactivation to ionize a defect to form a plurality of charge carriers.Further, in some embodiments, the application of elastic strain may beused to dynamically toggle the defect between a shallow dopant state anda deep dopant state rapidly and/or reversibly, akin to an ‘on-off’switch. Resultantly, in certain embodiments, a non-conducting defectdoped material with a large activation energy may transition to asemiconducting material or a conducting material with a lower activationenergy to ionize the defects upon the application of an elastic strain.Furthermore, the compositions and methods described herein can be usedto effectively n-dope and/or p-dope a material that was previouslyconsidered to be “undopable,” such that the material defects maytransition from a deep dopant state to a previously inaccessible shallowdopant state upon the application of elastic strain. In addition tosemiconducting and/or conducting devices, the defect doped materials maybe implemented in a memory device, due to the ability to dynamicallytoggle the defect doped material between these states.

In a conventional defect doped material, the ionization of defects leadsto the formation of one or more charge carriers (e.g., electrons and/orholes). For example, in some cases, a defect may have one or morelocalized electronic states that are within a bandgap and proximate tothe conduction band minimum and/or valence band maximum. The smaller theenergy gap between the localized electronic states and the conductionband minimum and/or valence band maximum, the less energy is used toionize the defects by thermal fluctuation energy at room temperature.FIG. 1A presents a schematic representation of a band structure of adefect doped material including a bandgap between a conduction band 112and valence band 114 with a bandgap energy 116 a As shown in the figure,a defect may have electronic state 118 within the bandgap and acorresponding activation energy 116 a to reach the conduction band edgeand/or valence band edge 112. In certain embodiments, the activationenergy may be too large to ionize the defect from the localizedelectronic state 114 to the conduction band edge and/or valence bandedge 112 by thermal fluctuation energy at room temperature.

FIG. 1B represents how applying an elastic strain to the material mayeither shift the band structure and/or the energy states of the materialdefects. For example, the electronic state 118 of the defects may movetowards the conduction band 112 of the band structure shown in FIG. 1A.Correspondingly, the resulting activation energy 116 c to ionize thedefects relative to the conduction band has been reduced by the appliedelastic strain. Of course embodiments, in which one or more of theconduction band, valence band, and/or energy state of the defects changerelative spacing, change shape, and/or change corresponding maxima andminima to reduce an associated activation energy to ionize the defectsare also contemplated. Thus, in some embodiments, the application of anelastic strain to a material may cause a defect in a material totransition into an excited electronic state (e.g, shallow dopant state)such that the activation energy- to ionize the defect to a conductionband edge and/or valence band edge is less than an activation energy ofthe defect in the unstrained state. Accordingly, the conducting state ofa defect doped material can be controlled by the application of strainto the defect doped material, such that the defect doped material maytransition from a non-conducting material to a semiconducting materialor a conducting material upon the application of strain due to thedecrease in the activation energy used to ionize the defects.

It should be understood that the disclosed methods of applying anelastic strain to alter the doping state of a defect doped material maybe applied to any of a variety of suitable compositions. For example, incertain embodiments the defect doped material may comprise defect dopeddiamond (e.g., carbon diamond), gallium oxide (Ga₂O₃), gallium nitride(GaN), boron nitride (BN), and/or any other appropriate material. Incertain embodiments, the defect doped material may be crystalline. Inother embodiments, the defect doped material may be at least partiallyamorphous. Additionally, appropriate dopants may include, but are notlimited to, nitrogen, boron, phosphorus, and/or combinations thereof. Ina certain non-limiting embodiment, a material comprising diamond isdefect doped with nitrogen. In such an embodiment, the diamond maycomprise about 1% nitrogen heteroatoms replacing carbon atoms.

According to certain embodiments, the amount of elastic strain that isapplied to a defect doped material to transition the material into adesired conductive state may be any of a variety of suitable amounts. Incertain embodiments, a strain is applied to a defect doped material inan amount between or equal to 1% and 25%. For example, in someembodiments, the elastic strain applied to the defect doped material maybe greater than or equal to 0.5%, 1%, 5%, 10%, 15%, and/or any otherappropriate amount of strain. In certain embodiments, the elastic strainmay be applied to the defect doped material in an amount less than orequal to 25%, 20%, 15%, 10%, 5%, 1%, and/or any other appropriate amountof strain. Combinations of the above recited ranges are also possible(e.g., the elastic strain may be applied to the defect doped material inan amount between or equal to 1% and 25%, 1% and 15%, 5% and 10%, and/orany other appropriate range including ranges both greater than and lessthan those noted above. It should be understood that these elasticstrain ranges may correspond to either compressive strains, tensilestrains, shear strains, and/or combinations of the forgoing such thatuniaxial, biaxial, and/or three dimensional elastic strains may beapplied to the disclosed materials. A variety of suitable methods ofapplying strain are further described in detail below.

The above noted strain ranges applied to a material may be measuredand/or calculated in a number of ways. For example, the elastic strainspresent in a material may be determined using finite element analysis,strain calculations using material geometries and applied deformations,strain calculations made using lattice mismatch considerations, straincalculations made using molecular dynamics simulations, straincalculations made by first-principles density functional theorysimulations, and/or any other appropriate method as the disclosure isnot limited to any particular method for evaluating the applied elasticstrains.

In certain aspects, a material may comprise a defect (e.g., a dopant).The defect may have the ability to be ionized into a charge carrier,such as an electron or a hole. For example, as shown in FIG. 2, acomposition 200 may correspond to a defect doped material 202 thatcomprises a defect 110 (e.g., a plurality of defects) The defects may beintroduced into the material by methods understood by one of ordinaryskill in the art. For instance, the defects may be implanted and/orgrown in the material during deposition of the material and/or thedefects may be formed after deposition of the material usingconventional techniques. Possible methods include molecular beamepitaxy, chemical vapor deposition, and/or other appropriate techniques.The defects may be evenly dispersed throughout the defect doped materialin some embodiments. How ever, in other embodiments, the defect dopedmaterial may comprise defects unevenly dispersed throughout the defectdoped material. For example, in some embodiments the defects may only bepresent in one or more isolated regions of the defect doped material.

In some embodiments, it may be desirable for a defect doped material tocomprise negative charge carriers (e.g., electrons) and/or positivecharge carriers (e.g., holes) depending on the functionality of thedefect doped material and/or what application it will be implemented in.Accordingly, a defect doped material may comprise a p-type dopant and/oran n-type dopant.

A defect doped material may comprise defects in any of a variety ofsuitable concentrations. The concentration of defects in the defectdoped material may depend on the material chosen (e.g., diamond, Ga₂O₃,BN, and the like). In certain embodiments, the defect doped materialcomprises defects in a concentration of less than or equal to 10³⁰ cm⁻³,less than or equal to 10²⁵ cm⁻³, less than or equal to 10²⁰ cm⁻³, lessthan or equal to 10¹⁵ cm⁻³, or less than or equal to 10¹⁰ cm⁻³, or lessthan or equal to 10⁵ cm⁻³. In some embodiments, the defect dopedmaterial comprises the defect in a concentration of greater than orequal to 10⁵ cm⁻³, greater than or equal to 10¹⁰ cm⁻³, greater than orequal to 10¹⁵ cm⁻³, greater than or equal to 10²⁰ cm⁻³, or greater thanor equal to 10²⁵ cm⁻³. Combinations of the above recited ranges are alsopossible (e.g., the defect doped material comprises defects in aconcentration of less than or equal to 10³⁰ cm⁻³ and greater than orequal to 10⁵ cm⁻³, the defect doped material comprises defects in aconcentration of less than or equal to 10²⁵ cm⁻³ and greater than orequal to 10¹⁵ cm⁻³). The concentration of the defects can be measured,in some embodiments, using experimental methods such as X-rayphotoelectron spectroscopy (XPS).

As described above, an activation energy may be associated with ionizingdefects to form a plurality of charge carriers, such as electrons and/orholes. According to some embodiments, the activation energy to ionizethe defects is an energy gap between one or more electronic states ofthe defect and the conduction band edge and/or valence band edge. Incertain instances, when the defect doped material is in an unstrainedstate, the activation energy of a defect may be sufficiently large suchthat it will not be ionized by thermal fluctuations of the material atordinary operating temperatures. In certain embodiments, such a largeactivation energy results in a defect doped material that isnon-conducting due to the large energy differential between the one ormore electronic states of the defect and either of the band edges.

In some embodiments, the activation energy- to ionize a defect of adefect doped material to form a plurality of charge carriers is greaterthan or equal to 1,000 meV when the defect doped material is in anunstrained state. For example, in some embodiments, the activationenergy- to ionize the defect is greater than or equal to 1,100 meV,greater than or equal to 1,200 meV, greater than or equal to 1,300 meV,greater than or equal to equal to 1,400 meV, or greater than or equal to1,500 meV when the defect doped material is in an unstrained state. Incertain embodiments, the activation energy to ionize the defect is lessthan or equal to 2,000 meV, less than or equal to 1,500 meV, less thanor equal to 1,400 meV, less than or equal to 1,300 meV, less than orequal to 1,200 meV, or less than or equal to 1,100 meV when the defectdoped material is in an unstrained state. Combinations of the aboverecited ranges are also possible (e.g., the activation energy to ionizethe defect may be greater than or equal to 1,000 meV and less than orequal to 2,000 meV when the defect doped material is in an unstrainedstate, the activation energy to ionize the defect may be greater than orequal to 1,200 meV and less than or equal to 1,800 meV when the defectdoped material is in an unstrained stale). Of course defect energies inthe unstrained state both greater and less than those noted above arealso contemplated.

In some embodiments, the activation energy to ionize defects of a defectdoped material to form a plurality of charge carriers is less than orequal to 200 meV when the defect doped material is in an elasticallystrained state. For example, in certain embodiments, the activationenergy to ionize the defect is less than or equal to 150 meV, less thanor equal to 100 meV, or less than or equal to 50 meV when the defectdoped material is in a strained state. In some embodiments, theactivation energy to ionize the defect is greater than or equal to 1meV, greater than or equal to 50 meV, greater than or equal to 100 meV,or greater than or equal to 150 meV when the material is in a strainedstate. Combinations of the above recited ranges are also possible (e.g.,the activation energy to ionize the defect may be less than or equal to200 meV and greater than or equal to 1 meV when the defect dopedmaterial is in a strained stale, the activation energy required toionize the defect may be less than or equal to 150 meV and greater thanor equal to 100 meV when the defect doped material is in a strainedstate). Of course embodiments in which the activation energy is eithergreater than or less than the range of activation energies noted abovefor a strained defect doped material are also contemplated as thedisclosure is not so limited.

Certain embodiments described herein may be related to a method ofcontrolling a conductive state of a defect doped material. Theconductive state of a defect doped material may be controlled, in someembodiments, by applying strain to at least a portion of the defectdoped material. FIG. 7 is, according to some embodiments, a flow chartdescribing a method of controlling a conductive state of a defect dopedmaterial. As shown in FIG. 7, a method of controlling a conductive stateof a defect doped material 700 may include step 702 comprising applyinga strain to at least a portion of a defect doped material. As a result,in some aspects, a corresponding composition may comprise a defect dopedmaterial with a strain applied to at least a portion of the defect dopedmaterial. According to some embodiments, the strain may be an elasticstrain.

As a result of applying strain to the defect doped material, the defectdoped material may transition from a non-conducting material to asemiconducting material or a conducting material. For example, as shownin FIG. 7, method 700 comprises step 704 where the defect doped materialtransitions from a non-conducting material to a semiconducting materialor a conducting material. Transitioning from a non-conductive materialto a semiconducting material or a conducting material may comprisedecreasing the activation energy to ionize the doped defects to form aplurality of charge carriers. Upon applying the strain to the defectdoped material, for example, the activation energy to ionize defects ofthe defect doped material to form a plurality of charge carriers maydecrease from a larger first energy (e.g., greater than or equal to1,000 meV) to a smaller second energy (e.g., less than or equal to 200meV).

Depending on the application of the defect doped material, it may bedesirable to selectively transition the material from the semiconductingmaterial or the conducting material back to a non-conducting material.Accordingly, in some embodiments, a strain may be removed from at leasta portion of an elastically strained defect doped material. For example,in certain embodiments, the defect doped material may be implemented ina semiconducting or conducting device where it is desirable to return toa deep dopant state from a shallow dopant state to change from asemiconducting material or a conductive material to a non-conductivematerial. This may have applications for switching, memory, or otherappropriate processes. In either case, the conductive state of a defectdoped material may be controlled, in some embodiments, by removing apreviously applied elastic strain from at least a portion of the defectdoped material as shown in FIG. 7 at step 706. As a result, in someaspects, a composition associated with the disclosed methods and systemsmay comprise a defect doped material where at least a portion of thedefect doped material is in an unstrained state during at least one modeof operation. For example, as shown at step 708, the defect dopedmaterial may transition from the semiconducting material or theconducting material to the non-conductive material. Transitioning fromthe semiconducting material or conducting material may correspond toincreasing the activation energy to ionize a defect to form a pluralityof charge carriers. Upon removing the strain from the defect dopedmaterial, for example, the activation energy to ionize defects of thedefect doped material to form a plurality of charge carriers mayincrease from a smaller energy (e.g., a shallow dopant state that isless than or equal to 200 meV) to a larger energy (e.g., a deep dopantstate that is greater than or equal to 1,000 meV). Accordingly, theconducting state of a defect doped material may be selectivelycontrolled by the selective removal and application of elastic strain toa defect doped material, such that the defect doped material mayselectively transition between a semiconducting material or a conductingmaterial and a non-conducting material.

As noted above, in some embodiments, it may be advantageous, tocyclically apply and remove strain to a defect doped material toselectively control a conducting stale of the defect doped material. Thecyclic application and removal of strain to control a conducting tostate of a defect doped material may be beneficial in applications suchas electronic switching components, memory devices, as well as otherapplications. Thus, in some embodiments the method 700 of FIG. 7 may becontinuously and selectively applied during operation of a device. Forexample, after the completion of step 708 where the material transitionsfrom the semiconducting material or conducting material to anon-conducting material, step 702 comprising applying a strain to atleast a portion of the defect doped material may be repeated, followedby steps 704-708 again. The cyclic application and removal of strain maybe performed any number of times and may be applied with any appropriatefrequency. For example, a first strain may be applied to the defectmaterial, followed by removal of the first strain from the defect dopedmaterial, followed by a second strain applied to the defect dopedmaterial, followed by removal of the second strain from the defect dopedmaterial, etc. In certain embodiments, the first strain, second strain,and/or any additional strains may be the same. How ever embodiments inwhich different amounts of strain are applied to a defect doped materialto provide different material properties during different operatingmodes are also contemplated as the disclosure is not limited in thisfashion.

While the above embodiment is directed to the cyclic application andremoval of strains to a defect doped material, the current disclosure isnot limited to only the cyclic application of strains to a defect dopedmaterial. For example, in some embodiments, the defect doped materialmay have a permanent or static elastic strain applied to maintain thedefect doped material as a desired semiconducting material or conductingmaterial.

The form of a defect doped material may, in some aspects, dictate howstrain is applied to and/or removed from the defect doped material.According to certain embodiment, the defect doped material may have anyof a variety of suitable forms (e.g., structures, sizes, and/or shapes).In some embodiments as shown in FIG. 2, a layer 200 may include a defectdoped material 202. However, the defect doped material may be providedin any appropriate form including, but not limited to, a planar layer, anon-planar layer, a rod, a needle, a filament, a three-dimensionalstructure with one or more holes, and/or any other appropriate structureas the disclosure is not limited to the specific geometry of a material.The disclosed materials may be provided in any appropriate fashion. Forinstance, a defect doped material may be an epitaxial layer grown on asubstrate, a standalone structure, a material that is transferred onto asubstrate, and/or any other appropriate construction as the disclosureis not so limited. Several non-limiting forms of the deposited materialsare discussed further below in greater detail.

In certain embodiments, at least a portion of a defect doped materialmay be in the form of a nanostructure (e.g., a nanowire, nanoparticle,nanosheet, nanorod, and the like). “Nanostructure” is used herein in amanner consistent with its ordinary meaning in the art. In certainembodiments, a nanostructure has a characteristic dimension, such as alayer thickness, or other appropriate dimension, that is between orequal to 1 nm and 1 micrometer. However, in other embodiments, at leasta portion of the defect doped material may be in the form of amicrostructure (e.g., microlayer, microwire, microparticle, microsheet,microrod, and the like). “Microscale” is used herein in a mannerconsistent with its ordinary meaning in the art According to certainembodiments, a microstructure may have a characteristic dimension, suchas a layer thickness, or other appropriate dimension, that is greaterthan or equal to 1 micrometer to less than or equal to 5 micrometers.Accordingly, in some embodiments, the disclosed materials may have acharacteristic dimension that is between or equal to 1 micrometer and 2micrometers, 10 nm and 1 micrometer, 10 nm and 500 nm, 10 nm and 100 nm,and/or any other appropriate length scale. Combinations of the abovecited ranges are also possible.

In some embodiments, a characteristic dimension, such as a thickness, ofa defect doped material can be measured electron microscopy techniques(e.g., scanning electron microscopy and/or transmission electronmicroscopy). The electron microscopy techniques can be supplemented by,for example, profilometry (e.g., optical or contact profilometers).

Having generally described the concept of applying an elastic strain toa material to alter its conductive properties, several methods foreither permanently, or selectively applying these strains are describedbelow. Generally, these methods may include both static and/or dynamicmethods of applying an elastic strain to a defect doped materialincluding, but not limited to, lattice mismatch during epitaxial growthof the material with a substrate, direct deformation of the materialwith an actuator or other structure, deformation of a substrate a defectdoped material is disposed on, and/or any other appropriate method ofapplying a desired elastic strain to the material.

In one embodiment, an elastic strain may be uniformly, or non-uniformly,applied to a defect doped material. In reference to FIG. 2, for example,a compressive strain 210 may be applied to a defect doped material 202.In some instances, this may be done hydrostatically as illustrated inthe figure where the same strain is applied to every external surface ofthe material. However, embodiments, in which non-uniform, in plane,three-dimensional, and/or any other appropriate form of elastic strainare applied to the material are also contemplated. For example,different elastic strains may be applied in different directionsrelative to the depicted material. This may include any desiredcombination of shear, tensile, compressive strains, and/or combinationsof the forgoing. This may be beneficial because the band structure anddefects of a material may respond differently to elastic strains appliedin different crystallographic directions.

As mentioned above, in some embodiments, a defect doped material may bedisposed on a substrate. For example, the defect doped material may bedisposed as a layer on the substrate. FIG. 3 is, according to someembodiments, a cross-sectional schematic representation of a defectdoped material layer disposed on a substrate. As shown in FIG. 3, alayer 300 comprises a defect doped material 202 comprising a pluralityof defects 110. In some embodiments, the defect doped material may bedisposed on a substrate 206. The defect doped material may be grown onthe substrate (e.g., grown on a single crystal silicon substrate).However, embodiments in which the defect doped material is separatelygrown and subsequently transferred onto the substrate are alsocontemplated. In certain embodiments, the defect doped material may beseparated from a substrate by any of a variety of suitable methods(e.g., lift-off processes, etching, and/or photofabrication techniquessuch as UV-curable adhesives). For example, in the case of anepitaxially grown material, a strain induced in the defect dopedmaterial due to lattice mismatch between the substrate and defect dopedmaterial may result in an in plane elastic strain 210 being applied tothe defect doped material as shown in the figure.

Similar to the above. FIG. 4 depicts an embodiment of a layer 400 ofdefect doped material 202 including a plurality of defects 110 disposedon a substrate 206. How ever, in the depicted embodiment, the substratemay include a recess 208 that underlies at least a portion of the layer.The recess may be formed by any of a variety of suitable means, such asetching (e.g., circuit board etching), microelectronic machining, and/orany other appropriate method. The recess may also pass either partially,or completely, through the substrate such that the layer extends atleast partially across the recess. In at least some instances, at leasta portion of the layer may extend all the way across the recess. Forexample, the layer may extend between two electrical contacts or otherstructures formed on either side of the recess. A recess such as thatshown in FIG. 4 may be formed for a number of reasons includingelectronic isolation of a corresponding portion of the defect dopedmaterial associated with the recess. To create the desired elasticstrain in the defect doped material 202, a strain 210 may applied to thesubstrate in some embodiments. This deformation may be either staticallyor selectively applied to the substrate and the associated defect dopedmaterial. In instances where the strain is selectively applied, thesubstrate may be selectively strained using an appropriate actuatorattached to the substrate, thermal expansion of the substrate,piezoelectric expansion of the substrate, and/or any other appropriatemethod of deforming the substrate. However, regardless of the specificmanner in which the substrate is deformed, as the substrate is deformed,the layer comprising the defect doped material may be elasticallystrained. Of course embodiments in which the strain deformation isapplied directly to both the substrate and the layer of defect dopedmaterial are also contemplated.

To aid in applying the desired elastic strains to the defect dopedmaterial noted above in reference to FIG. 4, in some embodiments, thelayer of material may have one or more stress concentrations formedtherein, to aid in focusing the strain in one or more desired portionsof the defect doped material. For example, a series of holes, notdepicted, may be formed in a layer of defect doped material to createportions of the defect doped material that are subjected to elevatedstresses and strains as compared to other portions of the defect dopedmaterial.

To facilitate the above noted deformation of a substrate, in someembodiments, a substrate may be made from a material that exhibits adesired amount of elasticity to accommodate applying the elastic strainsto the associated defect doped material. For example, in certainembodiments, the substrate may comprise a polymer such aspolydimethylsiloxane (PMDS), polymethyl methacrylate (PMMA),polycarbonate (PC), poly(ethylene glycol) diacrylate (PEGDA) polystyrene(PS), polyurethane (PU), and/or combinations thereof. However, in otherembodiments, the substrate may comprise conventional substrate materialssuch as metal oxide (e.g., an aluminum oxide such as sapphire, zincoxide, magnesium oxide and/or combinations thereof), silicon (e.g.,elemental silicon, silicon dioxide, silicon carbide and/or combinationsthereof), and/or any other appropriate substrate material.

In some embodiments a strain may be mechanically and/or dynamicallyapplied directly to a defect doped material. For example, in someembodiments, an elastic strain may be applied by deforming a defectdoped material with an actuator. FIG. 5 show's one such embodiment wherean actuator 214 is operatively associated with a defect doped material202 disposed on a substrate 206. As shown in FIG. 5, layer 500 comprisesthe defect doped material 202 with a plurality of defects 110. Theactuator 214 is in contact with a portion of the layer overlying arecess 208 formed in the substrate. In certain embodiments, the actuatoris a microelectromechanical (MEM) actuator. However, regardless of thespecific construction of the actuator, the actuator may be configured toselectively strain the defect doped material. For example, as shown inthe figure, the actuator may be configured to selectively apply adownwardly oriented strain 210 to a top surface 212 of the defect dopedmaterial located opposite the substrate and overlying the recess. Insome aspects, the actuator may be configured to selectively apply andremove the strain from the defect doped material in a cyclic fashion asdescribed above. For example, in some such embodiments, the actuator maybe configured to selectively strain the defect doped material to atleast a first strain. Additionally, the actuator may also be configuredto remove the first strain from the defect doped material, followed byan application of a second strain which may be greater than, equal to,or less than the first strain.

While a particular construction of an actuator for applying a strain toa layer of defect doped material has been illustrated in figures, itshould be understood that the current disclosure is not limited to onlythis particular embodiment. For example, different types of actuatorsand material layers with different geometries may be used as thedisclosure is not limited to this specific geometry and arrangement.

As explained herein, using strain to either statically and/orselectively control a defect doped material to have either a shallowdoping level and/or a deep doping level permits the creation of chargecarriers in the defect doped material. As a result, these defect dopedmaterials have the ability to transition from a non-conducting materialwhen in the unstrained state to a semiconducting or a conductingmaterial when in the elastically strained state. Accordingly, in someaspects, the defect doped materials disclosed herein may be beneficialfor use in forming at least a portion of a circuit. FIG. 6 is, accordingto some embodiments, a cross-sectional schematic representation of anon-limiting defect doped material forming at least a portion of acircuit. As shown in the figure, a circuit 600 comprises a componentmade from a defect doped material 202 comprising a plurality of defects110. The defect doped material may be disposed on a substrate 206. Insome embodiments, the defect doped material may be connected to one ormore electrical contacts (e.g., contact pads) 602, or other appropriatecomponent of the electrical circuit Other components of the circuit thatthe component made from the defect of material may be electricallyassociated with may include, but are not limited to, additional layers(e.g., passivation layer, metal layers), resistors, capacitors,transistors, inductors, and the like.

In view of the above, the compositions described herein comprising anelastically strained defect doped material may be used in a variety ofsuitable semi-conductor devices including, for example, photonicdevices, optoelectronic devices, high speed electronic devices,spintronic devices, photovoltaic devices, light-emitting devices (e.g.,light-emitting diodes or LEDs), and the like According to someembodiments, the defect doped material may be used as a memory device.As described herein, for example, a defect doped material may bedynamically toggled to permit or prevent the ionization of the defectsto form charge carriers due to the selective application of an elasticstrain. Thus, the defect doped material may be incorporated into amemory device due to the ability to cyclically toggle between one ormore localized electronic states of the defect and one or more excitedelectronic states. In such a memory device, the writing may compriseapplying strain, and the readout may comprise an electrical and/oroptical readout of the conductive state of the elastically strainedmaterial.

The following examples are intended to illustrate certain embodiments ofthe present disclosure, but do not exemplify the full scope of thedisclosure.

Example 1

The following example describes applying strain to a defect dopedmaterial comprising diamond.

The application of diamond as a semiconducting material or a conductingmaterial has historically been impeded by the difficulty toelectron-dope (e.g., n-type doping) the material. The nitrogen pointdefect (N_(C)) is bound to four carbon atoms (C-atoms) and hastetrahedral symmetry. There exists, however, a spontaneous symmetrybreaking of the tetrahedral symmetry to one of four equivalentlow-symmetry variants (N₁-N₄). In each symmetry variant, the nitrogenatom (N-atom) breaks a bond with one of the four C-atoms it is bound to,and forms shorter bonds with the other three C-atoms. A schematic of alow symmetry variant is shown in FIG. 8, wherein N-atom 804 is bound tothree C-atoms 802 a, but there is no bond between N-atom 804 and C-atom802 b. As a result, the nitrogen point defect is in a deep donor statethat is more than 1 eV below the conduction band edge. In such anenergetic state, the nitrogen point defect is impossible to ionize byroom-temperature thermal fluctuations and therefore will not contributecharge carriers to the conduction band.

In compressing when the diamond is elastically strained by as much as10%, the N₁-N₄ low symmetry variants are converted to N_(C) (Table 1)FIG. 9 shows, according to certain embodiments, a graph of the energybarrier as a function of strain. As strain is applied to the nitrogendoped diamond, the N-atom gradually moves to the center of thetetrahedral site bounded by four other C-atoms, until the crystal issymmetric. This process is shown in FIG. 10, which is a plot of thestrain gradient from an asymmetrical orientation to a symmetricalorientation for nitrogen doped diamond, according to some embodiments.The application of a 10% compressive strain creates a high symmetry,shallow donor state that readily contributes delocalized electroncarriers to the conduction band by thermal ionization. Furthermore,applying a compressive strain of 10% turns the energy barrier negative,which indicates the symmetric, tetrahedral structure is energeticallystable Applying a compressive strain to a region of diamond comprising anitrogen point defect can therefore provide a transition from a deepdopant state to shallow, n-type dopant state.

TABLE 1 Energy barrier decrease as strain is applied. Compressive strain(-%) Energy barrier (meV/atom) 0 9.465 0.5 9.141 1 8.752 2 7.907 3 6.9404 5.931 6 3.664 8 1.228 9 0 10 −1.713

1-16. (canceled)
 17. A method of controlling a conductive state of adefect doped material, the method comprising: applying a strain to atleast a portion of the defect doped material; and transitioning thedefect doped material from a non-conductive material to a semiconductingmaterial or a conducting material, wherein an activation energy toionize defects of the defect doped material in a strained state is lessthan the activation energy to ionize the defects when the defect dopedmaterial is in an unstrained state.
 18. The method of claim 17, whereintransitioning the defect doped material from the non-conductive materialto the semiconducting material or the conducting material comprisesdecreasing the activation energy to ionize defects of the defect dopedmaterial to form a plurality of charge carriers from a first energy thatis greater than or equal to 1,000 meV to a second energy that is lessthan or equal to 200 meV.
 19. The method of claim 17, wherein the strainis elastic strain.
 20. The method of claim 17, wherein the strain isapplied in an amount between or equal to 1% and 20%.
 21. The method ofclaim 17, wherein the strain is uniformly applied to the defect dopedmaterial.
 22. The method of claim 17, wherein the strain is only appliedto a portion of the defect doped material.
 23. The method of claim 17,wherein applying the strain includes deforming the defect doped materialwith an actuator.
 24. The method of claim 23, wherein the actuator is amicroelectromechanical actuator.
 25. The method of claim 17, whereinapplying the strain includes deforming a substrate the defect dopedmaterial is disposed on.
 26. The method of claim 17, wherein the defectdoped material comprises a p-type dopant.
 27. The method of claim 17,wherein the defect doped material comprises a n-type dopant.
 28. Themethod of claim 17, further comprising removing the strain from the atleast a portion of the defect doped material.
 29. The method of claim28, further comprising transitioning the defect doped material from thesemiconducting material or the conducting material to the non-conductivematerial.
 30. The method of claim 29, wherein transitioning the defectdoped material from the semiconducting material or the conductingmaterial comprises increasing the activation energy from the secondenergy that is less than or equal to 200 meV to the first energy that isgreater than or equal to 1,000 meV. 31-42. (canceled)
 43. A method ofcontrolling a conductive state of a portion of an electrical circuit,the method comprising: applying a strain to a defect doped materialforming at least a portion of the electrical circuit; and transitioningthe defect doped material from a non-conductive material to asemiconducting material or a conducting material, wherein an activationenergy to ionize defects of the defect doped material in a strainedstate is less than the activation energy to ionize the defects when thedefect doped material is in an unstrained state.
 44. The method of claim43, wherein transitioning the defect doped material from thenon-conductive material to the semiconducting material or the conductingmaterial comprises decreasing the activation energy to ionize defects ofthe defect doped material to form a plurality of charge carriers from afirst energy that is greater than or equal to 1,000 meV to a secondenergy that is less than or equal to 200 meV.
 45. The method of claim43, wherein the defect doped material comprises at least one selectedfrom the group of diamond, gallium oxide, gallium nitride, and boronnitride.
 46. The method of claim 43, wherein the defect doped materialcomprises nitrogen, boron, and/or phosphorus.
 47. The method of claim43, wherein the defect doped material comprises a p-type dopant and/oran n-type dopant.
 48. The method of claim 43, further comprisingapplying the strain to the defect doped material with an actuator.